Starting device for low voltage discharge tubes



NOV. 1935- E. A. LEDERER 2,020,731

STARTING DEVICE FOR LOW VOLTAGE DISCHARGE TUBES 2 Sheet-Sheet 1 Filed D96. 22, 1933 FIGJ FIGJ5 FIG.4

Pic-1.9

FIG.8

FIG.7

INVENTOR ERNEST A. LEDERER mi/Mat,

ATTQRNEY S Nov. 12, 1935. E LEDERER 2,020,731

STARTING DEVICE FOR LOW VOLTAGE DISCHARGE TUBES 2 Sheets- Sheet 2 Filed Dec. 22, 1955 FIGJU FIG."

FIGJZ -FI.G.I3 5 5% Is 5/? INVENTOR ERNEST A. LEDERER I QMWYM ATTORNEYS Patented Nov. 12, 1935 UNITED STATES PATENT OFFICE STARTING DEVICE FOR LOW VOLTAGE DISCHARGE TUBES Application December 22, 1933, Serial No. 703,541 In Austria December 24, 1932 8 Claims. (Cl. 175-124) Contrary to the well known incandescent lamp most of the luminous gaseous discharge tubes and in particular positive column lamps designed to operate from 60 to 600 volts cannot be made to operate by merely connecting their terminals to the source of electrical energy. In order to start operation of such tubes auxiliary equipment is required by means of which the passage of the electric current through the lamp is initiated or primed. Such equipment is usually termed a starting device and makes use, for instance, of a high voltage kick, irradiation of the tube by ultra-violet light, high frequency oscillations, or of auxiliary discharges in order to obtain the desired effect. Such starting devices as are known today require additional sources of sup ply and a complicated array of additional circuit members if operative at all. It is therefore impossible to start the operation of luminous dis charge tubes with the same case as isthe case with regular incandescent lamps by using only one switch. I

' The purpose of the present invention is to produce an entirely automatic apparatus to start and restart the luminous discharge in positive column tubes without necessitating any changes in their design or their physical properties or characteristics.

A satisfactory automatic starting should fulfill the following requirements. The starting device should function automatically as soon as the luminous tube is connected to the source of electrical energy although. it is desirable-that the starting device be inactive during the period of normal operation of the discharge tube. Positive operation of the discharge tube is required or in other words, the discharge tube must be given enough time to respond, without fail, to the influence of the starting device. Furthermore if the discharge tube "goes out during operation the starting device should then immediately become operative again in order to restart and restore the operation of the tube.

According to the present invention all of the above requirements are met because the starting device is rendered automatically operative by merely connecting the discharge tube and associated starting device to the source of electrical energy and it becomes automatically inoperative during the useful operation of the discharge tube. This may also be accomplished directly or indirectly and instantaneously or with time 'lag. Consequently the operation of the starting device is made dependent upon the condition of the gas discharge tube. By cond tion of the discharge tube is understood its physical state of whether or not the tube is in operation. Accordingly, it is provided that the starting device exerts its in-- fluence upon the discharge tube for such a length of time as may be required to put the latter in continuous sustained operation. After this is accomplished, and according to the present invention, the starting device is rendered automatically inoperative so that the operation oi! the discharge tube is in no way influenced or disturbed 10 by the presence of the starting device.

In order to influence the starting device to function in accordance with the above, its operation is made dependent upon the condition or upon one of the parameters of the main discharge circuit, provided that said parameter is influenced by the operation or interruption of the discharge tube.

The electrical circuit and connections are simplifled if the starting device and the discharge tube are energized from one and the same source of supply and operated from one and the same switch so that voltage is applied simultaneously on both starting device and discharge tube.

Usually the discharge tube or tubes have a falling or rising voltage characteristic which property can be conveniently utilized to control the operation of the starting device. If for instance, and this is usually the case, the current voltage characteristic is negative the common terminal voltage of the starting device and discharge tube is reduced with increasing discharge current. In such event the starting device may be designed, for instance, to become operative at or near the open circuit voltage, but inoperative at the reduced voltage at normal load. It is understood that open circuit voltage designates the potential difference existing at the terminals of the discharge tube if no current is passing through it. In case the characteristic of the discharge tube is "flat that is, the change in terminal voltage is small with rising discharge current, then other means like resistances, chokes or transformers can be used to provide for suflicient control of the starting device. It is furthermore understood that proper control of the starting device can be had with either rising or falling characteristics of the discharge tube.

For controlling the function of the starting device in the manner described it is necessary to make it sufliciently sensitive to variations in voltage. such as are encounteredduring actual operation ofthe discharge tube.

'Because of the various physical methods which can be used to initiate the discharge through a luminous tube the starting device may be designed utilizing either one or a combination of said methods. Likewise the control of the starting device can be effected in many ways, as for instance utilizing either current through the discharge tube, terminal voltage, temperature, emissive current, etc.

In order that the invention may be more clearly understood, reference is made to the accompanying drawings. The figures elucidate how the invention can be reduced to practice but it must be borne in mind that the examples given are only a few typical ones. The variations and the adaptability of the invention are too manifold to be described in all their details. In Figs. 1 to 13 inclusive, the gaseous discharge tube is indicated by the numeral I, its electrodes by the numerals 2, 2' which are connected to the terminals 5,5 of a source of electrical energy by the wires 3, 3'. A single pole single throw switch 4 provides for simultaneous connection of the discharge tube and the auxiliary starting device to the source of energy. Another circuit element referred to in several of the figures is an iron choke denoted by the numeral 6 which, as is well known, can be so designed that its impedance with high applied voltage is lower than its impedance with low applied voltage. Said iron choke, which may be replaced by any other impedance which resistance value is variable with either current or voltage, for instance a glow lamp, a gaseous rectifier, etc., is designed in such a manner that a considerable increase of the resistance value is produced if the terminal voltage on the electrodes of the discharge tube decreases. The circuit diagrams elucidated in Figs. 1 to 13 all refer to alternating current supply, for instance terminals 5, 5' can be connected. to v. or 220 v. A. C. 60 cycles. It is understood that with minor adjustments other voltages and other frequencies can be used. Furthermore with other adjustments direct current can be used as a source of energy. In Fig. l the starting device is designed as a high frequency generator. Parallel with tube l but in series with iron choke 6 is arranged an interrupter 1. Parallel to said interrupter and in series with the primary of a high frequency transformer 9 is a condenser 8. The secondary of the high frequency transformer or a conductor connected therewith is arranged in close proximity to the discharge tube l. The high frequency field of transformer 9 favorably affects the starting potentiaiof tube 1 in such a manner that a discharge through the latter is brought about because of the applied potential difference on its electrodes. In order to secure uniformity of operation, one terminal of the transformer 9 can be connected to a conductive collar Ill surrounding the discharge tube I at or about its middle portion. Its other terminal may be left floating or can be connected, for instance, to either one of the electrodes of the discharge tube. This simple circuit as described operates entirely automatically, closing switch 4, the open circuit potential is applied simultaneously on the electrodes of tube I and on the series combination of interrupter I and choke 6. The applied potential is insufiicient to start a discharge through tube I but it is ample to operate interrupter 'I through choke 6 because the latter is so designed to passthe operating current for interrupter I at said applied open circuit potential. By means of the operation of the interrupter high frequency currents are generated in the circuit comprising condenser 8 and transformer 8. Said high frepriming said tube becomes inactive.

quency currents applied on collar ll influence favorably the starting of tube I while voltage is applied to its terminals. Inversely with the increase of current through tube I the applied terminal voltage decreases to its final value termed hereinbefore the operating voltage. (The assumption is made that the tube I has, as indicated previously, a negative or falling characteristic.) At the operating voltage choke 6 only passes a very small current insufficient to energize interrupter I; hence the generation of high frequency current or the function of the starting device is terminated as soon as the discharge tube I is in continuous operation. Furthermore it is evident, that the entire process of operation repeats itself, if, for some reason the discharge through tube I is temporarily interrupted, thus the operationof the starting device is strictly automatic.

If for some reason, the initial priming of the 20 discharge tube is insufficient or its operation unstable, or in the event the discharge tube "goes ou suddenly without opening switch 4 then immediately operation of the interrupter and high frequency generation is re-established because choke 8 passes sufllcient current to operate the interrupter at the open-circuit voltage.

The described circuit using an interrupter may be changed for any other known source of high frequency generation. Special attention is called to the fact that any of such devices should be so designed and so dimensioned that they are put in operation above a certain minimum threshold value of energizing current. Also a circuit as described in Fig. 1 containing an interrupter can be changed in many ways, in order to adjust it to various requirements.

For instance, a circuit according to Fig. 2 may be selected with the advantage that in some cases. according to Fig. 1, only a small charge of condenser 8 or undesirable resonance effects may be produced by the capacitive current passing through said condenser. According to Fig. 2, the interrupter described above is provided with an auxiliary contact I, but the principal function of the entire circuit remains unchanged.

If it is desired not to use high frequency oscillations other methods for priming discharge tubes can be employed which serve the purpose as well without complications in the design of the start- 6 with interrupter I is arranged in parallel with discharge tube I. The interrupter in Fig. 3 cperates at a very low frequency and is so designed as to connect and disconnect automatically a capacitance II in parallel with tube I. Thereby capacitance II is discharged through a resistor l2. In closing switch I voltage is applied to tube I and because of the low impedance of choke 6 at this voltage, interrupter 1 is set in operation. Voltage kicks as produced in capacitance I I thus effect priming of the tube l. Similarly, as explained in connection with Fig. 1, at the operating voltage of tube I not enough current is passed through choke 6 to energize the interrupter I. so that automatically at beginning of normal operation of tube I the starting device Naturally interrupter I can be replaced by any other automatically controlled switching device.

Especially simple and advantageous, according to the invention, are such starting devices making use of automatically controlled resonance circuits. This group of circuits employs fundamentally a resonance circuit dependent and controlled by the condition of the discharge tube. Thereby one or more discharge tubes can be primed by the influence of a resonance circuit which in turn becomes inoperative or detuned as soon as current is flowing in the discharge tube or tubes.

This can be accomplished by arranging the tube and one member of a tuned series resonance circuit in permanent connection. By merely connecting this combination to the source of alternating current priming and starting of the discharge tube is accomplished. Fig. 4 elucidates the aforesaid principle. Two discharge tubes designated by numeral I are connected in series with each other and in parallel with a series resonance circuit comprising. a reactance (choke) I3 and a capacitance I4. The intermediate point I5 of the resonance circuit is conductively con nected to the conductive link It between the two discharge tubes I and I. Thus to each discharge tube there is one circuit element of the resonance circuit in parallel. In closing switch 4 a high voltage produced by the resonance circuit is impressed upon the terminals of the discharge tubes, which in turn effects starting of the latter. If current passes through the discharge tubes the resonance circuit is immediately detuned because of the current flowing in the tubes, a certain definite potential is impressed upon the intermediate point I5. By detuning the resonance circuit, only a small current will flow'through its circuit elements.

Furthermore during operation of tubes I, I, the voltage as applied to the terminals of the series resonance circuit is reduced hence the current passing through the latter is also reduced. It has been found that generally the current through the resonance circuit during operation of the discharge tube is about /5 of the current passing through it at full resonance. With certain apparatus the current at full resonance passing through the resonance circuit was. 0.25 amp. whereas through the detuned circuit only 50 milliamperes were flowing. This circuit arrangement is especially advantageous since it comprises only a few elements which can be permanently installed and which do not contain any moving parts. Otherwise circuit according to Fig. 4 can b changed in manifold ways. There exists no limitation as to the choice of the circuit elements of the resonance circuit and the special arrangements of intermediate point I5. Fig. 5 illustrates an example of the aforesaid in which three discharge tubes, connected in series with each other, are primed by a series resonance circuit, the latter consisting of three circuit elements. Naturally two intermediate points I5 will have to be connected to the conductive links l6 between the discharge tubes. It is now evident that two tubes for instance the first two at the left hand in Fig. 5 can be replaced by just one tube. In general it is only necessary that to each tube there is in parallel connection with it at least one circuit element of the resonance circuit.

For priming of a single discharge tube with the resonance method the use of auxiliary electrodes is sometimes of advantage. Such electrodes can be of the "internal or "external type, whereby the former is sealed air-tight into the glass vessel whereas the latter is preferably a piece of sheet metal or conductive coating in intimate contact with the outer wall of the discharge tube. External electrodes shaped like a collar and surrounding the middle portion of the discharge tube are'shown by the numeral III in Figs. 7 to 13. An internal auxiliary electrode is shown in Fig. 6 and designated 'by-the numeral II. In all such cases where an auxiliary electrode is employed it is always connected to an intermediate point, designated by the numeral I5, which is arranged between the capacitance H and the inductance I8. At resonance at sufficiently high voltage is developed at the auxiliary electrode to prime the discharge tube and start its operation. During operation of the discharge tube a certain potential is impressed by means of the auxiliary electrode upon the intermediate point thus detuning the resonance circuit and consequently reducing the current through the latter. In Figs. 6 and 7 the auxiliary electrode is directly and conductively connected to the intermediate point I5 of the resonance circuit. A capacitive coupling 'of auxiliary electrode and intermediate point by means of a condenser I8 is shown in Fig. 8. The advantage of this arrangement lies in the fact that danger, when touching the auxiliary electrode, is reduced. The same object can be accomplished by substituting a resistance choke etc. for the condenser and naturally the electrical dimensions must be so chosen as to provide for maximum safety. when using a condenser I8 of .001 to .01 mt. in aoircuit like Fig. 8 and 220 v. A. 0. applied to terminals 5, 5 it was found that this capacitance was sufficient to safeguard uniform operation of the discharge tube at the same time considerably reducing danger when collar I is touched accidentally. In Fig. 9 the secondary of a transformer I9 is arranged in series with the auxiliary external electrode I0 and the intermediate point I5. The primary of transformer I9 is in series with the discharge tube and the electrical constants of the transformer are so selected as to counteract partially or completely the high voltage impressed upon collar I0 by means of the resonance circuit after the discharge has started. It is obvious that the same arrangement can be utilized if instead of one discharge tube as in Fig. 10. two or more discharge tubes are used. For instance, referring to Figs. 4 and the secondary of the counteracting transformer would be connected in series with the conductive link I6 and the intermediate point I5.

No limitation is imposed upon the addition of other circuit elements in combination with the starting devices according to the present invention,.as may be required when using discharge tubes of various characteristics. For instance, connection with the resonance circuit (see point 2|, Figs. 6 and 7) can be made before (see Fig. 6) or after (see Fig. 7) the series resistance 20 in Figs. 6 and 7 as may be used with discharge tubes having negative characteristics. Another special circuit is shown in Fig. whereby two discharge tubes I, I are connected in series between the corner points 2| and 22 of a bridge resonance circuit, which other corner points 23 and 24 are connected to the auxiliary electrodes of the discharge tubes.

The invention can be utilized to start discharge tubes with cold or heated electrodes but the advantages and usefulness is particularly great in connection with the latter. In using tubes with indirectly heated electrodes still more advantages will be found because the heater circuits can then be included in the automatic features of the starting device. According to a further variation of the invention the automatic priming can be closely associated with a process depending upon the heating of the electrode of the discharge tube. There are two methods possible in carrying this out. One uses the change in heating current and the other the change in the emission current to control the function of thestarting device. The first method can be furthermore subdivided in two special cases. In the first case the heating current exerts its full infiuence immediately, after it is turned on, upon the starting device. In the second case the final stationary value of the heating current, after cathode or heater are in temperature equilibrium. is used to control the operation of the starting device.

In Figs. 11 to 13 various examples of circuits are elucidated which make use of the controlling influence of the heater current. It is hardly necessary to emphasize specifically that the number of examples can be increased at will, because according to the invention principally every important circuit element can be put under the influence of the heating current. In many cases the coordination between heater current and control of the starting device is of special advantage, because a time lag in the actual priming of the discharge tube can be effected. This time lag is often desired in connection with the use of hot electrodes, since uniformity of starting and absence of flickering is thereby safeguarded. Another advantage of the time lag is, that the coating on the electrodes is protected against sputtering and abuse, because the priming voltage is appliedonly after the electrodes are heated to their operating temperature.

The circuit shown in Fig. 11 is a modification of that in Fig. 1. Arranged in series with the heater filament 25, of an indirectly heated hot cathode in tube I is the primary of a current transformer 26 which secondary is shorted through an additional coil 21 on choke 6. Thereby the windings of coil 21 and of coil 26 are so dimensioned that the choke 6 is considerably demagnetized if the heater current is large in magnitude while warming up the indirectly heated electrode. Being demagnetized to a considerable extent the impedance of choke 6 is so large, that the interrupter 1 cannot begin to function as long as the electrode is in the status of warming up. If at the end of the warming up period the heater current diminishes tending to attain its stationary operating value, the demagnetizing influence of said current upon choke 6 is reduced causing the choke to pass more current which in turn operates the interrupter I. From then on the function of the starting device progresses exactly in the same manner as explained in connection with Fig. 1 above. This special circuit can be modified of course in manifold ways. For instance, instead of demagnetizing choke 6, coil 27 can be made to act likewise directly upon the interrupter 1, thus bucking the current which would ordinarily flow through 1. Another modification of the circuit shown in Fig. 11 may consist for instance in the elimination of the current transformer 26, arranging coil 21 directly in series with the heater filament.

Fig. 12 shows how the emission current from the hot electrode 2 can be utilized to control the function of the starting device. In proximity with hot electrode 2 there is sealed into the discharge tube an auxiliary electrode (anode) 29 which is connected to the other terminal of the discharge tube through an additional coil 31 wound on choke 6. Therefore it switch 4 is closed, full open circuit potential prevails between electrode 2 and auxiliary starting electrode 29. As soon as an emission current flows from 2 to 29 and through coil II, which current can be 5 adjusted if desired by resistance 30, it will act by means of coil 3i upon the choke 6, tending to saturate the iron in the choke, thereby causing an increase of current through the choke which in turn is sufllcient to operate the interrupter I. 10 The function of the remaining part of the circuit has been explained already, it being remembered that the starting device stops operation automatically as soon as the flow of current through tube I causes a decrease of terminal potential and there- 15 by a decrease of current through said choke 6. Furthermore it may be pointed out that by using indirectly heated electrodes the heater filament or one of its lead wires or a suitable extension thereof may be used instead of auxiliary eleczo trode 29.

Fig, 13 exemplifies how priming by resonance can be controlled by the heating up or by the emission process, if indirectly heated electrodes are used. The series resonance circuit comprises 25 the capacitance 32, the inductance 33 andan iron choke 34. This choke 34 is provided with two additional windings 35 and 36, each of which is coordinated with one of the two hot electrodes of the discharge tube in such manner that the emis- 30 sion current of each cathode passes through its respective winding. Thus the circuit of ti". one cathode comprises the elements 2, 25, 36, 31, 3 and that of the other cathode comprises the elements 2',-25', 36, 31, 3. Furthermore windings 35 35 and 36 are so arranged that the emission currents exert respectively a magnetizing and demagnetizing influenceupon choke 36. The series resonance circuit is so adjusted that full resonance is only obtained if the finite operating 40 emission current passes through windings 35 and 36. Priming of the tube and detunlng oi the series resonance circuit has been explained in the previous examples.

Referring to Figs. 11, 12 and 13 terminals of 45 heaters for the unipotential indirectly heated cathodes are denoted by numerals 38, 39 and 36, 39'. It is understood that said terminals must be connected with a suitable source of electrical energy, for instance the secondary windings of a 5 transformer 40, but for simplicity it is not shown in the drawings.

It is further understood that in Figs. 1 to 13 excluding Figs. 6 and '7, a suitable ballast impedance must be used between either one of the 55 terminals 5, and 5' and the source of energy if discharge tubes with negative characteristic are used. Also this ballast resistance is not included in the drawings except in Figs. 6 and '1 for simplicitys sake. 60

It is now obvious that a large number of examples could be added to those described without departing from the true spirit and scope of my invention. The possibilities of combination of the circuit principles exemplified herein are man- 55 ifold. The choice between the various circuits is determined by the construction of the discharge tube, its special properties, the source of energy and many other circumstances.

What is claimed is:

1. In combination, a plurality of electric gaseous discharge devices in series, an impedance in series with said devices, a condenser connected in parallel with one of said devices and a reactance connected in parallel with the other, said imped- 1 ance, condenser and reactance being in series resonance when no current is flowing through said discharge devices.

2. In combination, an electric gaseous discharge device having a pair of main electrodes and an auxiliary starting electrode, an impedance connected in series with said device, a condenser connected between one of said main electrodes and said auxiliary electrode, and a reactance connected between the other oi said main electrodes and said auxiliary electrode, said impedance, condenser and reactance being in series resonance when no current is flowing through said device.

3. In combination, an electric gaseous discharge device having a pair of main electrodes and an auxiliary starting electrode, an impedance in series with said device, a condenser and reactance connected in series in parallel with said device, said impedance, condenser and reactance being in series resonance when no current is flowing through said device and a condenser connected in series between said auxiliary electrode and a point between said first mentioned condenser and reactance.

4. In combination, an electric gaseous discharge device having a pair of main electrodes and an auxiliary starting electrode, a series resonant circuit having an element connected between one of said main electrodes and said auxiliary electrode through one winding of a transformer, the other winding oi said transformer being connected in series with said discharge device, whereby the potential applied to said auxiliary electrode is reduced when current flows through said device.

5. In combination, a pair of electric gaseous discharge devices having a pair of main electrodes and an auxiliary starting electrode, said devices being connected in series between diagonal corners or a series resonant bridge which consists oi alternate reactors and condensers, the remaining corners of said bridge being connected to said auxiliary electrodes.

6. In combination, an electric gaseous discharge device having a pair of main electrodes, at least one of which is a thermionic cathode, means 5 to impress an abnormal potential on said device to initiate a discharge therein, said last mentioned device including a saturable reactance whose value controls the operation of said means, and means to vary the saturation of said reactance in accordance with variations in the temperature of said cathode, whereby the application of said abnormal potential is delayed until the cathode has reached a temperature at which the thermionic emission therefrom will support the normal discharge current without destructive hot-spotting.

7. In combination, an electric gaseous discharge device having a pair of main electrodes at least one of which is a thermionic cathode, means comprising a series resonant circuit to apply an abnormal potential to said device to initiate a discharge therein, and means responsive to the temperature of said cathode to detune said resonant circuit until said cathode has reached a temperature at which the thermionic emission will support the normal discharge current without destructive hot-spotting.

8. In combination, an electric gaseous discharge device having a pair of main electrodes of which, at least one is a thermionic cathode, and an auxiliary starting electrode, a series resonant circuit having an element thereof connected between said auxiliary electrode and one of said main electrodes, and means responsive to the temperature of said cathode to detune said resonant circuit until said cathode has reached a temperature at which the thermionic emission will support the normal discharge current without destructive hot-spotting.

ERNEST ANTON LEDERER. 

